Kokopo Cardinalfish

Last July, I was on MV Golden Dawn just off Kokopo, which is the center of activity in the Rabaul area of East New Britain, PNG these days, given that Rabaul town is covered in ash and there is regular volcanic activity spewing dust, red-hot rocks, ash and noxious fumes into the air and onto Rabaul.

We were moored just off shore, with a muck bottom about 20m to 25m below. Everyone else geared up and went for a wreck dive. I chose to stay behind, and dived down on the mooring line to look around.

A bunch of discarded tires were part of the mooring set up, and around/ inside/ among the tires were substantial communities of life...eels, stonefish, cleaner shrimp and lots of fish.


Given that it was two days before full moon, I kept my eyes open for courtship activity, which tends to happen around full and new moons. Sure enough, there were a couple of species of cardinalfish around the tires, both engaging in mating rituals. A few were carrying eggs, perhaps fertilised around the previous new moon.

With murky water, swarms of fish, plus tires/ chains/ ropes flopping all over the place, it took many(!) tries to isolate a single fish. This one had an enormous mouthful of eggs, ripe enough that I could easily make out the baby eyes.

In case you don't know, male cardinalfish care for fertilised eggs in their mouths, occasionally spitting them out to aerate them, which is what's going on in the picture below.

aerating eggs

Both photos shot at f8, 1/200, ISO160 on a Canon Eos 5D with a 100mm macro lens, plus two Inon Z220 strobes.

Can anyone help me ID the species?

Update 28 Jan: I think we've determined it's an Apogon apogonides, common name plain cardinalfish. Thanks Ron!